Spinal fusion device

ABSTRACT

A spinal fusion device is disclosed. The spinal fusion device includes a first endplate configured for fitting within a disc space and engaging with a first vertebra and a second endplate configured for fitting within the disc space and engaging with a second vertebra. The two endplates are separated by a single spacer that is positioned between the first endplate and the second endplate and maintains a pre-determined distance between the first endplate and the second endplate. The spacer contains an anterior end, a posterior end, a first lateral side, a second lateral side opposite to the first lateral side, a first surface that engages with the first endplate, a second surface that engages with the second endplate. Also disclosed are methods and instruments for implanting the spinal fusion device.

RELEVANT APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 13/207,041, filed on Aug. 10, 2011, which is acontinuation-in-part application of U.S. patent application Ser. No.12/618,930, filed on Nov. 16, 2009, which claims priority of U.S.Provisional Application Ser. No. 61/114,636, filed on Nov. 14, 2008. Theaforementioned applications are hereby incorporated by reference intheir entirety.

TECHNICAL FIELD

The technical field is medical devices and, more particularly, spinalfusion devices.

BACKGROUND

The vertebral column, or the spinal column, is composed of a series ofconnected bones called “vertebrae.” The vertebrae surround the spinalcord and protect the spinal cord from damage. Nerves branch off thespinal cord and travel to the rest of the body, allowing forcommunication between the brain and the body. The vertebrae areconnected by spongy intervertebral discs. The intervertebral disc, whichis made up of strong connective tissues that hold one vertebra to thenext, acts as a cushion or shock absorber between the vertebrae.

Spinal fusion is a surgical procedure used to correct problems with thevertebrae and/or intervertebral disc, such as degenerative disc disease,spinal disc herniation, discogenic pain, weak or unstable spine causedby infections or tumors, vertebral fracture, scoliosis, kyphosis,spondylolisthesis, spondylosis, Posterior Rami Syndrome, and otherdegenerative spinal conditions that causes instability of the spine.

In a typical spinal fusion procedure, the intervertebral disc ispartially or fully removed. Although a number of spinal fusion deviceshave been developed, there still exists a need for a spinal fusiondevice that is capable of maintaining the height and the naturallordosis of the spine, and that can easily be assembled and dissembledin a surgical procedure.

SUMMARY

A spinal fusion device is disclosed. The spinal fusion device includes afirst endplate configured for fitting within a disc space and engagingwith a first vertebra, a second endplate configured for fitting withinsaid disc space and engaging with a second vertebra, and a single spacerconfigured for sliding between the first and the second endplates in ananterior to posterior direction, causing the endplates to be separatedin a direction generally perpendicular to said sliding direction. Thespacer comprises: an anterior end; a posterior end; a first lateralside; a second lateral side, opposite to the first lateral side; a firstsurface that engages with the first endplate; a second surface that isopposite to the first surface and engages with the second endplate. Thefirst endplate is locked to the spacer by a locking device comprising aspring-loaded plunger in the spacer and a corresponding recess in thefirst endplate, wherein the spring-loaded plunger protrudes from thefirst lateral side of the spacer.

Also disclosed is a method for implanting the spinal fusion device in asubject. The method comprises preparing a disc space between twoadjacent vertebrae; inserting a first endplate and a second endplateinto the disc space, wherein each endplate comprises an anterior end, aposterior end, a locking recess, and spikes on an outer surface;inserting a spacer between the pair of endplates, wherein the spacercomprises an anterior end, a posterior end, a first surface that engageswith the first endplate, a second surface that engages with the secondendplate, a first lateral side, a second lateral side opposite to thefirst lateral side, and a spring-loaded plunger having a plunger endprotruding from the first lateral side; and advancing the spacer betweenthe pair of endplates towards the posterior end of the endplates untilthe plunger end self-locks into the locking recess on at least one ofthe first end plate and the second end plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention,and the manner of attaining them, will become more apparent and theinvention will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein corresponding reference charactersindicate corresponding parts throughout the several views and wherein:

FIG. 1 is a front view of an embodiment of a spinal fusion device;

FIG. 2 is a top view of the spinal fusion device of FIG. 1;

FIG. 3A is a side view of the spinal fusion device of FIG. 1;

FIG. 3B is a side view of an endplate of the spinal fusion device 1;

FIG. 4A is a front view of adjacent vertebral bodies with the spinalfusion device of FIG. 1 disposed therebetween;

FIG. 4B is a cross sectional view of the adjacent vertebral bodies andthe spinal fusion device of FIG. 1 taken along line A-A of FIG. 4A;

FIG. 5 is a perspective view of a spacer which forms part of the spinalfusion device of FIG. 1;

FIG. 6 is a top view of the spacer of FIG. 5;

FIG. 7A is a front view of the spacer of FIG. 5;

FIG. 7B is cross sectional view of the spacer of FIG. 5 taken along lineB-B of FIG. 7A;

FIG. 7C is an enlarged cross sectional view of the flexible tab of FIG.7B;

FIG. 8A is plan view of the inner surface of an endplate of the spinalfusion device of FIG. 1;

FIG. 8B is a front view of the endplate of FIG. 8A;

FIG. 8C is plan view of the inner surface of another embodiment of anendplate of the spinal fusion device of FIG. 1;

FIG. 8D is a front view of the endplate of FIG. 8C;

FIG. 8E is a front view of a spacer with sliding ends that match thecenter dovetail slot of the endplate of FIG. 8C;

FIG. 9A is a side view of a tapered spacer which can form part of the ofthe spinal fusion device;

FIG. 9B is a top view of a spacer with cross bars at both the anteriorand posterior ends;

FIG. 10 is a perspective view of another embodiment of a spinal fusiondevice;

FIG. 11 is a perspective view of an endplate of the spinal fusion deviceof FIG. 10;

FIG. 12 is a top view of the endplate of FIG. 11;

FIG. 13 is a bottom view of the endplate of FIG. 11;

FIG. 14 is a front view of the endplate of FIG. 11;

FIG. 15 is a cross sectional view of the endplate of FIG. 14 taken alongline C-C;

FIG. 16 is a perspective view of a spacer which forms part of the spinalfusion device of FIG. 10;

FIG. 17 is a top view of the spacer of FIG. 16;

FIG. 18 is a side view of the spacer of FIG. 16;

FIG. 19 is a top view of the spinal fusion device of FIG. 10;

FIG. 20 is a cross sectional view of the spinal fusion device of FIG.19, taken along line D-D;

FIG. 21 is a flow chart showing an embodiment of a method for implantingthe spinal fusion device;

FIG. 22 is a perspective view of an embodiment of an endplate inserter;

FIG. 23 is a side view of the endplate inserter of FIG. 22;

FIG. 24 is a top view of the endplate inserter of FIG. 22 coupled withthe engaging endplates of the spinal fusion device;

FIG. 25 is a partial section view, taken along line E-E of FIG. 24, ofthe engaging endplates coupled with the endplate inserter;

FIG. 26 is perspective view of the endplate inserter, the spinal fusiondevice, and a driver coupled together;

FIG. 27 is a perspective view of an embodiment of a spacer inserter;

FIG. 28 is a perspective view of the spacer inserter of FIG. 27 coupledwith a spacer according to the present invention;

FIG. 29A is a perspective view of the endplate inserter, the spacerinserter, and the assembled spinal fusion device coupled together;

FIG. 29B is a perspective view of the endplate inserter, the spacerinserter, the assembled spinal fusion device, and the splaphammercoupled together;

FIG. 30 is a side view of the endplate inserter, the spacer inserter,and the spacer being inserted between the engaging endplates;

FIG. 31 is a perspective view of a thin endplate trial;

FIG. 32 is a perspective view of an implant construct trial;

FIG. 33 is a perspective view of an endplate inserter used to insertendplates shown in FIGS. 11 and 12;

FIG. 34 is a side view of the endplate inserter of FIG. 33;

FIG. 35 is a top view of the endplate inserter of FIG. 32 coupled withthe engaging endplates of the spinal fusion device of FIG. 10;

FIG. 36 is a partial section view, taken along line F-F of FIG. 35, ofthe engaging endplates coupled with the endplate inserter;

FIG. 37 is a perspective view of an embodiment of a spacer inserter;

FIG. 38 is a perspective view of the spacer inserter of FIG. 37 coupledwith the spacer of FIG. 16;

FIG. 39 is a side view of the endplate inserter, the spacer inserter andthe spacer being inserted between the engaging endplates;

FIG. 40 is a view of detail circle J in FIG. 39;

FIG. 41 is a perspective view of the endplate inserter, the spacerinserter and the assembled implant coupled together;

FIG. 42 is a perspective view of a slap-hammer;

FIG. 43 is a perspective view of the assembled implant, the endplateinserter, and the slap-hammer coupled together;

FIG. 44A is a perspective view of another embodiment of a spinal fusiondevice;

FIG. 44B is a top view of the spinal fusion device of FIG. 44A;

FIG. 45 is a side view of adjacent vertebral bodies with the spinalfusion device of FIG. 44A disposed therebetween;

FIG. 46 is plan view of the inner surface of an endplate of the spinalfusion device of FIG. 44A;

FIG. 47 is a front view of an endplate of the spinal fusion device ofFIG. 44A;

FIG. 48 is a side view of an endplate of the spinal fusion device ofFIG. 44A;

FIG. 49 is a perspective view of a spacer of the spinal fusion device ofFIG. 44A;

FIG. 50A is a side view of a spacer of the spinal fusion device of FIG.44A;

FIG. 50B is an enlarged view of the flexible tabs of FIG. 49;

FIG. 51 is a side view of the endplate inserter coupled with theendplates being inserted in between the adjacent vertebrae using alateral approach;

FIG. 52 is a top view of the endplate inserter coupled with theendplates being inserted in between the adjacent vertebrae using alateral approach;

FIG. 53 is a perspective view of the spacer of FIG. 49 attached with anembodiment of a spacer inserter;

FIG. 54 is a side view of the endplate inserter, spacer inserter of FIG.53 coupled with the spacer of FIG. 49 showing the spacer being insertedbetween the engaging endplates;

FIG. 55 is a top view of the endplate inserter, spacer inserter of FIG.53 coupled with the spacer of FIG. 49 showing the spacer being insertedbetween the engaging endplates;

FIG. 56 is a perspective view of the assembled fusion implant of FIG.44, the endplate inserter, and a slap-hammer coupled together;

FIG. 57 is a perspective view of an embodiment of a spacer with arotating locking device;

FIG. 58 is a top view of the spacer with a rotating locking device;

FIG. 59 is a perspective view of a rotating pin used in the spacer witha rotating locking device;

FIG. 60 is a front view of the spacer with a rotating locking device;

FIG. 61 is a top view of an endplate used with the rotating lockingdevice;

FIG. 62 is a perspective view of a spacer-endplate assembly with therotating locking device in a locked position;

FIG. 63 is a perspective view of a spacer-endplate assembly with therotating locking device in an unlocked position;

FIG. 64 is a perspective view of an embodiment of a spacer with aspring-loaded locking device;

FIG. 65 is an exploded front view of the spacer with a spring-loadedlocking device;

FIG. 66 is an exploded perspective view of the spacer with aspring-loaded locking device;

FIG. 67 is an exploded perspective view of a plunger used in thespring-loaded locking device;

FIG. 68 is a top view of a spacer-endplate assembly with thespring-loaded locking device;

FIG. 69 is a perspective view of another embodiment of a spacer with aspring-loaded locking device having a position pin;

FIG. 70 is an exploded perspective view of a plunger used with thespring-loaded locking device of FIG. 69;

FIG. 71 is another perspective view of the spacer with the spring-loadedlocking device of FIG. 69;

FIG. 72 is a top view of a spacer-endplate assembly with thespring-loaded locking device of FIG. 69 in an unlocked position;

FIG. 73 is a perspective view of a spacer-endplate assembly with thespring-loaded locking device of FIG. 69 in an unlocked position;

FIG. 74 is a perspective view of a spacer-endplate assembly with thespring-loaded locking device of FIG. 69 in a locked position;

FIG. 75 is an isometric view of an embodiment of a spacer containing analternate mechanism used to lock the spacer with the endplates of thespinal fusion device;

FIG. 76 is an exploded front view of an embodiment of a spacer and thespring loaded plunger mechanism;

FIG. 77 is an exploded isometric view of the spacer in FIGS. 75 and 76;

FIG. 78 is an isometric view of the bottom of an endplate;

FIG. 79 is an exploded isometric view of the spring loaded plungermechanism in FIG. 76;

FIG. 80 is an isometric view of an assembled interbody fusion implantwith a spacer locked with endplates using a spring loaded plungermechanism;

FIG. 81 is a side view of the assembled interbody fusion implant of FIG.80;

FIG. 82 is an exploded isometric view of an embodiment of a spacer;

FIG. 83 is an isometric view of the bottom of an endplate;

FIG. 84 is an exploded isometric view of a spring loaded plungermechanism;

FIG. 85 is an isometric view of an assembled interbody fusion implant;

FIG. 86 is a side view of the assembled interbody fusion implant of FIG.85;

FIG. 87 is a view of a bone graft delivery system;

FIG. 88 is a view of a bone graft delivery system of FIG. 87 with thevial released from the dispensing device;

FIG. 89 is an isometric view of the bone graft delivery system of FIG.87 interfaces with as assembled implant;

FIG. 90 is a side view of the bone graft delivery system of FIG. 90;

FIG. 91 is a side view of an assembled implant construct with asymmetricendplates;

FIG. 92 is an isometric view of an assembled extreme lateral approachimplant;

FIG. 93 is a side view of the assembled implant of FIG. 92; and

FIG. 94 is an exploded isometric view of the assembled implant of FIG.92.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the invention may be practiced. It isto be understood that other embodiments may be utilized and structuralor logical changes may be made in alternate embodiments. Therefore, thefollowing detailed description is not to be taken in a limiting sense,and the scope of embodiments in accordance with the present invention isdefined by the appended claims and their equivalents.

This description is intended to be read in connection with theaccompanying drawings, which are to be considered part of the entirewritten description of this invention. The drawing figures are notnecessarily to scale and certain features of the invention may be shownexaggerated in scale or in somewhat schematic form in the interest ofclarity and conciseness. In the description, relative terms such as“horizontal,” “vertical,” “up,” “down,” “top,” “bottom,” “outer,”“inner,” “front,” “back,” “anterior,” and “posterior,” as well asderivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,”etc.) should be construed to refer to the orientation as then describedor as shown in the drawing figure under discussion. These relative termsare for convenience of description and normally are not intended torequire a particular orientation. Terms including “inwardly” versus“outwardly,” “upwardly” versus “downwardly,” “longitudinal” versus“lateral” and the like are to be interpreted relative to one another orrelative to an axis of elongation, or an axis or center of rotation, asappropriate. Terms concerning attachments, coupling and the like, suchas “connected” “interconnected,” “coupled,” “engaged” and “attached”refer to a relationship wherein structures are secured or attached toone another either directly or indirectly through interveningstructures, as well as both movable or rigid attachments orrelationships, unless expressly described otherwise. The term“operatively connected” is such an attachment, coupling or connectionthat allows the pertinent structures to operate as intended by virtue ofthat relationship.

Embodiments of a spinal fusion device that provides column support tothe spine and facilitates a fusion between adjacent vertebral bodies aredisclosed. In certain embodiments, the fusion device includes threepieces, namely, a pair of endplates configured to be attached tovertebrae flanking a vertebral disc space, and a single spacerpositioned between the two endplates and releasably attached to the twoendplates to maintain the endplates in a lordotic alignment.

In an embodiment, the endplates of the fusion device are shaped to matchthe general shape of the vertebral body and to inhibit subsidence intothe vertebra. The outer faces of the pair of endplates containprojections that extend into and engage with the end of vertebrae. Theprojections reduce migration of the device within the disc space afterengagement with the end of vertebrae. The endplates include a variety ofopenings to allow bone to grow through the endplates. The endplates mayinclude one or more slots with a dovetail-shaped cross section. The oneor more slots extend from the anterior end of the endplates to theposterior end of the endplate, and are sized to receive thecorresponding sliding plate or plates of the spacer. As usedhereinafter, the “anterior end” of an end plate is the end from whichthe spacer is inserted between two endplates.

In this embodiment, the spacer has a shape that generally matches theshape of the mating endplates. The spacer has two arms connected by acrossing bar at the posterior ends or at both the posterior ends andanterior ends. The spacer is used to distract the endplates duringinsertion and is always inserted between the two endplates in ananterior-to-posterior direction.

In an embodiment, the spacer contains one or more flexible tabs thatinterface with corresponding slots on the engaging endplates to lock thespacer to the endplates. The flexible tab/slot design allows the spacerto be locked into the endplates without the use of lockinginstrumentation. In another embodiment, each endplate contains one ormore flexible tabs that interface with corresponding slots on thesurface of the spacer to lock the endplate to the spacer.

In an embodiment, the flexible tab also contains a sloped sidewall thatallows the spacer to be disengaged from the endplates by pulling thespacer with sufficient force in the posterior-to-anterior direction, soas to dissemble an implanted fusion device in situ.

The top and the bottom surface of the two arms of the spacer may containdovetail-shaped sliding plates to interface with the corresponding slotson the endplates. During the assembling process, the spacer is insertedbetween the pair of endplates in the anterior-to-posterior direction.Once fully engaged with the endplates, the single piece spacer providessupport to endplates along lateral, anterior, and posterior aspects ofthe fusion device to share axial compressive loads. In one embodiment,the spacer includes an opening proximate the anterior end for placing abone graft or other filling materials after it has been assembled withinthe intervertebral space.

In an embodiment, the top and bottom surfaces of the spacer aresubstantially parallel to each other, so as to separate the endplatesfrom each other in a parallel fashion. A lordotic angle is createdthrough various angles created in the engaging endplates.

In an embodiment, the height of the spacer is designed to vary along thelength in the anterior-posterior direction, such that the height betweenthe anterior end of the spacer is greater than the height between theposterior end of the spacer. In this embodiment, the lordotic angle iscreated by the spacer and not through various angles created in theengaging endplates.

In an embodiment, the lordotic angle is created by both the endplate andthe spacer. The modular design of the spinal fusion device allows forthe device to be customized to fit a particular patient's anatomy. Thespinal fusion device can be used in the lumbar spine and in the cervicalspine as well.

FIGS. 1-9 show embodiments of a spinal fusion device 10. As shown inFIGS. 1 and 2, the assembled device 10 has an anterior end 20, aposterior end 22 and two sides 40 and 42. The device 10 generallyincludes endplates 12 and 14 and a spacer 24 sandwiched between theendplates 12 and 14. The outer surfaces 16 and 17 of the endplates 12and 14 are shaped similar to the natural shape of the vertebral body toprovide a relatively large contact area between the endplates and theinterfacing vertebral bodies. The contact force between the vertebraeand the endplates is imparted over a large surface area and hencereduces the risk of subsidence of the fusion device 10 into thevertebrae. In this embodiment, the outer surface 16 or 17 of endplates12 or 14, respectively, has a slightly convex shape to conform to theconcave end surfaces 19 and 21 of vertebrae 47 and 48, as shown in FIG.4B. As shown in FIG. 2, the outer surfaces 16 and 17 of the endplates 12and 14 may contain a variety of openings 26 and 30 to allow bone growththrough the endplates 12 and 14 and between the adjacent vertebrae 47and 48 shown in FIGS. 4A and 4B.

Referring now to FIG. 3A, the outer surfaces 16 and 17 of the endplates12 and 14 may contain multiple spikes 36 protruding from the outersurfaces 16 and 17 to anchor the endplates 12 and 14 to the end surface19 and 21 of corresponding vertebrae 47 and 48 (see FIG. 4B). The spikes36 extend into the body of vertebrae 47 and 48 to prevent migration ofthe fusion device 10 within the disc space after implantation. Thespacer 24 is engaged with both endplates 12 and 14 and maintains thedistance between two endplates. Spacers of different thickness may beused to create spinal fusion devices with desired height (i.e., a heightthat matches the height of the disc space in which the spinal fusiondevice is implanted).

In order to maintain the natural lordotic angle of the spine, thethickness of the spinal fusion device 10 may vary from the anterior end20 to the posterior end 22. As shown in FIG. 3A, the spinal fusiondevice 10 has a posterior height 18 defined by the distance between theouter surfaces 16 and 17 at the posterior end 22 of the endplates 12 and14, and an anterior height 34 defined by the distance between the outerfaces 16 and 17 at the anterior end 20 of the endplates 12 and 14. Theanterior height 34 is greater than the posterior height 18 in order tomaintain the natural lordotic angle of the spine. In this embodiment,the different heights at the anterior end and the posterior end isachieved by varying the thickness of the endplates 12, 14 at theanterior end 20 and the posterior end 22. FIG. 3B shows an endplate witha built-in lordotic angle 4. FIGS. 4A and 4B show the positioning of animplanted spinal fusion device 10.

The implanted spinal fusion device 10 may be filled with bone graft tofacilitate the growth of bone through the fusion device. A bonesubstitute material, such as demineralized bone matrix, calciumphosphate, calcium sulfate or synthetic bone substitute materials, canalso be packed within the fusion device. The bone graft is placed withinthe central cavity 82 of spacer 24 (see FIG. 5) before the spacer 24 isinserted between the endplates 12 and 14.

In one embodiment, the spacer 24 has an open anterior end, as shown inFIG. 9B, that allows insertion of the bone graft after the spacer asbeen assembled with the engaging endplates. This embodiment of thespacer 24 may further contain an optional retaining plate that isattached to the anterior end of the spacer 24 after the insertion of thebone graft to prevent migration of bone graft after implantation.

Referring again to FIG. 1, the spacer 24 provides support to theengaging endplates and provides a predetermined spacing between theouter surfaces 16 and 17 of plates 12 and 14. The predetermined spacingis approximately equal to the height of the disc material that occupiedthe disc space between the vertebral bodies when the disc was healthy.As shown in FIG. 1, the spacer 24 may include two arms 44 and 46 thatextend between the plates 12 and 14 along the length of the spinalfusion device 10 from the anterior end 20 to the posterior end 22.

As shown in FIGS. 5 and 6, the arms 44 and 46 may be substantiallyparallel to each other and are connected at both the posterior andanterior ends by connectors 66 and 69, respectively. The connectors 66and 69 help share the load with the engaging endplates 12 and 14 and thearms 44 and 46 of the spacer 24. The connectors 66 and 69 also preventmigration of bone graft from the spinal fusion device in the posteriorand anterior directions. As shown in FIG. 7A, the thickness of theconnectors 66 and 69 may be defined as the spacer height (h_(s)). Theconnector 69 may further contain notches 51 to allow clearance for tabson a spacer inserter 114 as it is being released after the implant hasbeen assembled. Each arm may contain one or more flexible locking tab62, a sidewall 56, and a side pocket 60. As shown in FIG. 7A, threadedhole 67 and slot 68 in the anterior side of spacer 24 allow for apositive attachment with the spacer inserter 114 shown in FIG. 27.Threaded hole 67 of spacer 24 attaches with the corresponding threadedrod 121 of spacer inserter 114. Slot 68 of spacer 24 may engage with acorresponding pin 123 of spacer inserter 114 to prevent rotation of thespacer after it has been attached to the spacer inserter.

With continued reference to FIGS. 6 and 7A, the arm 44 of the spacer 24may include a pair of sliding ends 50 and the arm 46 of the spacer 24includes a pair of sliding ends 52. The sliding ends 50 and 52 have endwidths 54 and 58, respectively, that are greater than the width of themidsection of the arms 44 and 46, thus forming dovetail shaped slidingends 50 and 52 that fit into the corresponding slots 70 on the endplates12 and 14. Once assembled, the edges of the dovetail shaped sliding ends50 and 52 engage with the side walls of the dovetail shaped slots 70 andhold the spacer and the corresponding endplate together. In anembodiment, the dovetail shaped sliding ends 50 and 52 and have a lengththat is the same as the length (L_(a)) of the arms 44 and 46. In certainembodiments, the length L_(a) may be about 50%-80%, 55%-75%, 60%-70% or66%-67% of the overall length (L_(b)) of the spacer 24.

As shown in FIG. 6, sliding ends 50 and 52 may contain only a partialdovetail (i.e., a dovetail section 61 that is shorter than the length(La) of the arms 44 and 46) to aid in assembly with the engagingendplates during insertion. Specifically, the partial dovetail designmakes it easier for a surgeon to adjust the position of the spacer 24between the endplates 12 and 14 and engage the spacer 24 with theendplates 12 and 14. With a portion of the dovetail removed, shown as 64in FIG. 6, this portion of arms 44 and 46 enters the mating dovetailslots 70 in endplates 12 and 14 first while the spacer is being used todistract the endplates, which may not be parallel. This design thusallows the spacer 24 to extend in between the endplates 12 and 14 in aposterior direction and thus separate the endplates 12 and 14 in aparallel fashion, before the dovetails 61 of the spacer 24 engage withthe mating dovetail slots 70 of endplates 12 and 14. In certainembodiments, the length 61 may be about 25%-50%, 30%-45%, 33%-40% or36%-37% of the overall length (L_(b)) of the spacer 24.

FIG. 7B shows a cross-section of an embodiment of the flexible lockingtab 62. The flexible locking tab 62 may include a cantilever structure55 formed over a space 53. The cantilever structure 55 contains aprotrusion 59 that locks into the locking slot 38 on endplates 12 and14. The protrusion 59 contains a sloped front wall 64 that allows thecantilever structure 55 to be depressed into the space 53 when thespacer 24 is pushed into the space between the endplates 12 and 14 inthe anterior-to-posterior direction. The cantilever 55 bounces back whenthe protrusion 59 reaches the locking slot 38 and self-locks into thelocking slot 38. Such a design renders it possible to assemble thespinal fusion device 10 in situ by inserting the endplates 12 and 14into a disc space and then inserting the spacer 24 between the twoendplates and advancing the spacer 24 towards the posterior end of theendplates until the flexible locking tabs 62 on the spacer 24 lock intothe corresponding lock slots 38 on the endplates.

In certain embodiments, the protrusion 59 may also contain a sloped backwall 65 that allows the protrusion 59 to be disengaged from the lockingslot 38 by pulling the spacer 24 in the posterior-to-anterior directionwith sufficient force. The sloped back wall 65 makes it possible todissemble an implanted spinal fusion device in situ by pulling out thespacer 24 and then remove the endplates 12 and 14. Such a releasabledesign allows a surgeon to remove the spinal fusion device or to replacethe endplate/spacer with an endplate/spacer of different size or height.

As shown in FIG. 7C, the front wall 64 of the protrusion 59 forms anangle 57 with the top surface of the spacer and the back wall 65 of theprotrusion 59 forms an angle 63 with the top surface of the spacer. Incertain embodiments, the angle 57 is in the range of about 120-170degrees, preferably 135-160 degrees, and the angle 63 is in the range of95-135 degrees, preferably 105-120 degrees. In another embodiment theangle 63 is about 90 degrees and does not allow the spacer 24 to bedisengaged from the endplates when a force is applied to spacer 24 inthe posterior-to-anterior direction.

The number and position of the flexible locking tab 62 may vary invarious designs of the spinal fusion device 10. In certain embodiments,the flexible locking tab 62 are formed on the endplates and lock intocorresponding slots formed on the spacer.

With reference now to FIGS. 8A and 8B, the slots 70 may be sized toaccommodate the dovetail shaped sliding ends 50 and 52 of the spacer 24and hold the spacer 24 in place. The spacer 24 can be coupled to theengaging endplates 12 and 14 by sliding the sliding ends 50 and 52 intothe slots 70 in the anterior-to-posterior direction. The flexible tab 62is pressed downward into space 53 (FIG. 7B) during the insertion processuntil the tab 62 reaches and locks into the slot 38 of the engagingendplate. The endplate 12 further contains a dovetail shaped slot 72that engages with an endplate inserter during the assembling process.The inner surface 15 of endplate 14 is substantially similar to that ofthe endplate 12.

FIGS. 8C and 8D show another embodiment of the end plates 12 and 14. Inthis embodiment, each endplate may contain one large centered dovetailslot 84 as opposed to two side dovetail slots 70 for engaging with thespacer 24. Specifically, the sidewalls 85 and 86 of the dovetail slot 84interact with the edges 87 and 88 of the sliding ends 50 and 52,respectively, thus coupling the spacer 24 to the endplate. The inserterdovetail slot 72 is formed above the centered dovetail slot 84. FIG. 8Eis a front view of a spacer 24 with sliding ends that match the centereddovetail slot 84 of the endplate.

The engaging endplates 12 and 14 may have substantially identical ordifferent lordotic angles. In certain embodiments, the lordotic angle ofthe fusion device 10 is created by the endplates 12 and/or 14. Thespacer 24 may has have the same predetermined height along the length ofsliding ends 50 and 52. Spacers 24 of different heights (h_(s)) may beused to assemble with the engaging endplates 12 and 14 to allow theassembled construct height to be custom fit to various patient discspace heights.

In other embodiments, the lordotic angle of the fusion device is createdby the spacer 24. FIG. 9A shows a taped single spacer 24 with variableheight along the length of sliding ends 50 and 52. When this spacer 24is positioned between the engaging endplates 12 and 14, the height ofthe assembled fusion device 10 decreases in a direction from theanterior end 20 to the posterior end 22 to maintain the natural lordoticangle of the human spine. The predetermined angle 48 of the spacer 24corresponds to the desired lordotic angle of the patient at the affectedlevel.

Referring now to FIGS. 10-20, there is shown another embodiment of aspinal fusion device 400. As shown in FIG. 10, the spinal fusion device400 generally includes two identical endplates 200 and a spacer 300therebetween. The spinal fusion device 400 may be used in the cervicalspine through an anterior approach, or sized to be used in the lumbarspine as well. In this embodiment, the endplates 200 are designed with ashape to fit the ends of adjacent cervical vertebrae.

Referring now to FIGS. 11-15, each endplate 200 may contain a flexibletab 210 for locking into a corresponding slot 320 on the spacer 300 anda series of projections 220 extending from the outer faces 215 of therespective endplate 200 for fixation of the engaging plates 200 with thecervical vertebral endplates. The endplate 200 may also contain a pairof side dovetail slots 250 on its inner surface 225 to receive thecorresponding dovetail sliding plates on the spacer 300 and a centerdovetail slot 230 to receive the corresponding structure on the endplateinserter. As shown in FIG. 15, the flexible tab 210 extends into theslot 250. The sloped front wall 235 of the flexible tab 210 allows thetab to be pushed upward while the spacer 300 is being assembled with theendplates 200 and to lock into the corresponding structures on thespacer 300 in a full assembled spinal fusion device. In this embodiment,the tab 210 has an end wall 245 that is substantially perpendicular tothe inner surface 225 of the endplate 200. In other embodiments, the tab210 has a sloped end wall 245. In certain embodiments, the front wall235 forms an angle 257 of about 120-170 degrees, preferably 135-150degrees with the inner surface 225. In other embodiments, the end wall245 forms an angle 263 of 95-135 degrees, preferably 105-120 degreeswith the inner surface 225.

Referring now to FIGS. 16-18, the spacer 300 may contain two arms 340,and connectors 350 and 365 that connect the arms 340 at the posteriorand anterior ends respectively. As shown in FIG. 18, the outer surfaces360 and 370 of the arms 340 form an angle 310 to maintain the naturallordotic angle in the cervical spine. Since the lordotic angle iscreated with the spacer 300, the engaging endplates 200 may beessentially flat. The spacer 300 contains a slot 320 on each arm 340 tocaptures the flexible tab 210 of the engaging endplates 200 duringassembly to lock the spacer 300 to both the top and bottom engagingendplates 200. In this embodiment, one slot 320 is located on the outersurface 360 of one arm 340 and another slot 320 is located on theopposite outer surface 370 of another arm 340 so as to receive theflexible tab 210 from each endplate 200. The spacer 300 may furthercontain a side pocket 330 in each arm 340 to receive a correspondingstructure on the spacer inserter. The connector 365 may further containnotches 351 to allow clearance for tabs on a spacer inserter as it isbeing released after the implant has been assembled.

A completely assembled spinal fusion device 400 is shown in FIGS. 19 and20. The cross-sectional view of the device (FIG. 20) shows that thespacer 300 creates the desired lordotic angle. As noted earlier, whilethe tab 210 shown in FIG. 20 has an end wall 245 that is substantiallyperpendicular to the inner surface 225 of the endplate 200, the tab 210may have a sloped end wall 245 so that an implanted fusion device 400may be dissembled in situ by pulling the spacer 300 out of the engagedposition with sufficient force that disengages the tab 210 from thepocket 320.

The endplates of the spinal fusion devices may be constructed with abiocompatible material with sufficient strength. Examples of suchmaterials include, but are not limited to, metals such as titanium,stainless steel, cobalt-chromium-molybdenum, titanium alloy and otheralloys, polymers such as polyetheretherketone (PEEK), ceramics,composites such as carbon fiber reinforced PEEK. In one embodiment, theendplates are constructed with a titanium alloy, such as atitanium-aluminum-vanadium alloy.

Similarly, the spacers of the spinal fusion devices may be constructedwith a biocompatible material with sufficient strength. Examples of suchmaterials include, but are not limited to, metals such as titanium,stainless steel, cobalt-chromium-molybdenum, titanium alloy and otheralloys, polymers such as polyetheretherketone (PEEK), ceramics,composites such as carbon fiber reinforced PEEK. In one embodiment, thespacer is constructed with polyetheretherketone.

In some embodiments, surfaces of the engaging plates and/or spacer thatcontact bone may include a coating to promote osteointegration of theimplant with bone. Examples of the coating include, but are not limitedto, a titanium plasma spray, hydroxyapatite, or a bone morphogeneticprotein.

In another embodiment, the spacer and/or endplates are made with aradiolucent material to allow the bone fusion mass to be seen onradiographic images.

Also disclosed are an instrumentation set and methods for implanting aspinal fusion device between adjacent vertebral bodies. Theinstrumentation set may include trial endplate and trial components, anendplate inserter, spacer inserters, hex drivers, and slap hammers.Trial components may be of various sizes and lordotic angles. Anendplate inserter may be used to place the endplates between adjacentvertebral body after a discectomy has been performed. A spacer may beattached to a spacer inserter to guide the spacer through the endplateinserter.

With reference to FIG. 21, shown is an embodiment of a method 2100 forimplanting embodiments of the spinal fusion device. To installembodiments of the spinal fusion device, a block discectomy may beperformed with an anterior approach or a lateral approach. In ananterior approach, a surgical exposure of spine is created by passingthrough or going behind the abdominal cavity. In a lateral approach, thesurgical exposure of spine is created by passing through the psoasmuscle (transpsoas). The method 2100 may include preparing (block 2102)a spinal disc space between two adjacent vertebrae by removing theintervertebral disc along with anterior osteophytes adjacent to theinterspace. The removing may be done using various techniques known inthe art. The method 900 further includes determining (block 2104) theappropriate size endplate footprint using a thin endplate trial anddetermining (block 2106) the appropriately sized implant using animplant construct trial. As shown in FIG. 31, an endplate trial 140 is athin plate that is used to determine the appropriate size of endplate inorder to maximize endplate coverage of the ends of adjacent vertebraeand reduce the chance of subsidence. As is well known to a person ofordinary skill in the art, patients of different sizes and weight mayrequire endplates of different sizes. A thin endplate trial 140 may beprovided for each endplate footprint. FIG. 32 depicts an implantconstruct trial 150. A construct trial corresponds to the actualfootprint, thickness, and lordotic angle between the vertebra formed bythe assembly of the endplates with the spacer. The implant constructtrial 150 allows a surgeon to select the appropriately sized implant tocustom match the patient's own disc space. The surgeon is able to testevery combination of implant that can be formed with engaging endplatesand spacers.

An endplate inserter may be operationally coupled (block 2108) with apair of endplates so that endplates may be inserted (block 2110) intothe spinal disc space. A spacer may be coupled (block 2112) to a spacerinserter so that the spacer may be inserted (block 2114) into a lumen ofthe endplate inserter. When inserting the spacer, the spacer is advanced(block 2116) towards the posterior end of the endplates until the locktabs on the spacer lock into the corresponding lock slots on theendplates. The spacer inserter is decoupled (2118) from the spacerinserter and the endplate inserter is decoupled (2120) from theendplates. The method may further include inserting bone graft or bonesubstitute into a central portion of the spinal fusion device.

FIGS. 22 and 23 depict an embodiment of an endplate inserter 100. Theendplate inserter 100 includes a handle 102 and flexible arms 104 thathold a pair of endplates. The handle 102 includes a lumen 106 that issized to allow the insertion of a spacer between the endplates with aspacer inserter 114 (see FIG. 29A). Each arm 104 may include a couplingplate 108 that can be removably attached to an endplate. In oneembodiment, the coupling plate 108 is a dovetailed plate that matches toa corresponding female dovetail slot 72 on the endplate (as shown inFIGS. 8A and 8B). The coupling plate 108 may further include tabs 110that engage with the slot 26 of the endplate 12 or 14 to lock theinserter 100 to the endplate 12 or 14. FIG. 24 depicts an endplateinserter 100 with endplate 12 attached to the flexible arms 104.

The arms 104 of the endplate inserter 100 are flexible to allow them tobend so spacers 24 of varying pre-determined heights can be passedthrough the inserter 100 and inserted between the engaging endplates 12and 14. The inserter 100 may include a threaded screw 112 to allow tabs110 to be opened or closed. When the screw 112 is advanced, the tab 110is in the locked position that engages with the slot 26 of theendplates, thus securing the endplates 12 and 14 to the endplateinserter 100. When the screw 112 is backed out, the tab 110 isdisengaged from the slot 26 to allow the inserter 100 to be separatedfrom the endplates 12 and 14. The notch 51 in the spacer 24 allows anopening for the tab 110 to pass through the spacer 24 after the tab 110is disengaged from the endplates 12 and 14 (See FIGS. 5 and 7A). Asshown in FIG. 26, a driver 130 may be used to turn the screw 112 todisengage the tab 110 of the endplate inserter 100 from the slot 26 ofthe engaging endplates.

FIG. 27 depicts a perspective view of a spacer inserter 114. The spacerinserter 114 includes a rotating threaded shaft 121 and a fixed pin 123,a inserter body 124, and a turning knob 122. The threaded shaft 121 maybe rotated by turning knob 122 and thus engaging the threaded shaft withthe threaded hole 67 in spacer 24. The fixed pin 123 of spacer inserter114 engages with the mating slot 68 of spacer 24 to prevent the spacerfrom rotating once it has been coupled with the spacer inserter 114.FIG. 28 shows a perspective view of the spacer 24 coupled with thespacer inserter 114.

Referring now to FIGS. 29A, 29B and 30, the body 124 of the spacerinserter 114 interfaces with the lumen 106 of endplate inserter 100 asdepicted in the perspective view of FIG. 29. The clearance between thebody 124 and the lumen 106 is minimized to provide a controlled deliveryof the spacer 24 through the endplate inserter 100 and into the engagingendplates 12 and 14. Surface 128 of the spacer inserter 114 is an impactsurface for interface with a mallet during the insertion of the spacer24 between the endplates 12 and 14. Slots 125 of spacer inserter 114 areused to couple the inserter with a slap-hammer 160 to allow an impulseforce to be applied to the spacer 24 to disengage the flexible tab 62from the engaging slot 38 of the endplates 12 and 14, thus allowing thespacer to be removed from the endplates after assembly within the discspace. FIG. 29B shows the slap-hammer 160 attached to the spacerinserter 114.

FIG. 30 depicts a view of the spacer 24 entering the space between theendplates 12 and 14. In FIG. 30, the spacer 24 is not yet locked intothe endplates 12 and 14, but has been sufficiently advanced into thespace between the endplates 12 and 14 to separate the endplates into asubstantially parallel position to allow engagement of the dovetails 61of the sliding ends 50 and 52 with the corresponding slots 70 (not shownin FIG. 30) on the endplates 12 and 14. Separation of the endplates 12and 14 by the spacer 24 may force projections 36 on the outer surfacesof the engaging plates into the boney end of the adjacent vertebrae toattach the endplates 12 and 14 to the body of the vertebrae (FIG. 4B).

While the instrumentation in FIGS. 22-32 is shown only with spinalfusion device 10, it is understood that the instrumentation set and thesurgical procedure described above and shown in FIGS. 22-32 can also beused to insert the spinal fusion device 400 within the cervical orlumbar spine.

FIGS. 33 and 34 show another embodiment of an endplate inserter 500.Similar to the endplate inserter 100, the endplate inserter 500 mayinclude a handle 502 and flexible arms 504 that hold a pair of endplates200. The handle 502 includes a lumen 506 that is sized to allow theinsertion of a spacer between the endplates with a spacer inserter 514.Each arm 504 includes a coupling plate 508 that can be removablyattached to an endplate 200. In one embodiment, the coupling plate 508is a dovetailed plate that matches to a corresponding female dovetailslot 230 on the endplate 200 (shown in FIG. 14). The coupling plate 508may further include flexible tabs 510 that engages with the slot 226 ofthe endplate 200 to lock the inserter 500 to the endplate 200. Theflexible tabs 510 are pressed downward during the insertion processuntil the tabs 510 reaches and lock up into the slot 226 of the engagingendplates 200. Slots 525 allow the attachment of a slap-hammer to theendplate inserter 500 to remove the endplate inserter 500 from anassembled spinal fusion device 400. FIG. 35 shows the endplate inserter500 coupled the endplates 200. FIG. 36 is a partial cross sectional viewalong the line F-F of FIG. 5 showing the coupling mechanism between theendplates 200 and the endplate inserter 500.

FIG. 37 depicts a perspective view of another embodiment of spacerinserter 514. The spacer inserter 514 may include a pair of arms 520 tohold the spacer 300, an inserter body 524, and a turning knob 522. Thearms 520 may include tabs 516 that couple with slots 330 of a spacer 300(see FIG. 16). The tabs 516 allow the spacer 300 to be coupled with aspacer inserter 514. FIG. 38 shows a perspective view of the spacer 300coupled with the spacer inserter 514. The arms 520 of the spacerinserter 514 may be spread wider by turning knob 522, thus increasingthe distance 526 between tabs 516. Turning knob 522 in the oppositedirection will shorten the distance 526 between the tabs 516 to providea clamping force to the sides 335 of the spacer 300.

Referring to FIGS. 39 and 40, the body 524 of the spacer inserter 514interfaces with the lumen of the endplate inserter 500. Surface 528 ofthe spacer inserter 514 is an impact surface for the interface with amallet during the insertion of the spacer 300 between the endplates 200.The impact is passed to the spacer 300 through the surfaces 518 of thearms 120 to advance the spacer 300 between the engaging endplates 200.FIG. 41 shows the spacer 300 completely engaged and locked with theendplates 200 after the fusion device has been assembled in situ.

Referring now to FIGS. 42 and 43, the endplate inserter 500 may beremoved from the endplates 200 after the interbody construct 400 hasbeen assembled by attaching a slap-hammer 560 to the endplate inserter500 and applying an impulse force to disengage the tabs 510 from theslots 226 in the endplates 200. A slot 351 in the spacer 300 allows anopening for the tab 510 to pass through the spacer 300 after the tab 510is disengaged from the endplates 200 (See FIGS. 16 and 17).

Referring now to FIGS. 44A-50B, shown are various diagrams and viewsillustrating another embodiment of a spinal fusion device 600. As shownin FIG. 44A, the spinal fusion device 600 generally includes twoendplates 700 and the spacer 800 therebetween. The spinal fusion device600 can be used in the lumbar spine through a lateral approach. In thisembodiment, the endplates 700 are designed with an outer surface 760 tobe convex in shape to generally fit the concavity of the adjacentvertebral boney surface. FIG. 44B shows a top view of the endplate 700.FIG. 45 shows adjacent vertebral bodies with the spinal fusion device600 disposed therebetween.

FIG. 46 shows the inner surface of the endplate 700. Each endplate 700may contain two openings 710 for a bone graft to grow through theendplate 700 and allow fusion with an adjacent vertebrae, an edge 725which provides a surface to engage with flexible tabs 810 of spacer 800,two central dovetail slots 720 and 730 to couple with the endplateinserter 900 and the spacer 800. The dovetail slots 720 and 730 may becentered on the bottom surface 740 of the endplate at two differentdepths so the spacer 800 can couple with the mating dovetail slot 720 inendplate 700 while simultaneously allowing an endplate inserter to beengaged with the dovetail slot 730 in the endplate. As shown in FIG. 47,which shows a side view of the end plate 700, the endplate 700 containsa series of projections 750 extending from the outer faces 760 of theendplates 700 for fixation of the engaging plates 700 with the lumbarvertebral bodies. The flexible tab 810 extends into the larger opening710 while the surface 735 prevents the spacer 800 from accidentaldisengagement from the endplates 700 after assembly. The sloped wall 820of the flexible tabs 810 allows the tabs 810 to be pushed away from theengaging endplate 700 while the spacer 800 is being assembled with theendplates. Once the flexible tab 810 enters the larger opening 710 inendplate 700, the flexible tab 810 snaps into the opening to lock theendplates 700 with the spacer 800 therebetween, as shown in FIGS. 44Aand 44B.

FIGS. 49-50B show various views of the spacer 800, as shown in FIG. 49,the spacer 800 may contain sliding ends 840 and 850. The width 860 ofsliding surfaces 840 and 850 are greater than the width of themidsection of the spacer 800, thus forming dovetail shaped sliding ends840 and 850 that fit into the corresponding slots 720 of the endplates700. The lead-in width 865 of the spacer 800 may be less than thedovetail width 860 to allow the spacer to slide in between the endplates700 during initial assembly and separate the endplates 700 in a parallelfashion before the sliding ends 840 and 850 of spacer 800 engage withthe corresponding dovetail slots 720 of endplates 700. In certainembodiments, the dovetail surfaces 840 and 850 have a length L_(c) thatmay be about 20%-60%, 25%-50%, 30%-45% or 32%-40% of the overall length(L_(d)) of the spacer 800. FIG. 50A shows a front view of the spacer800.

Referring again to FIGS. 49 and 50A, slots 870 at the anterior end ofthe spacer 800 allow clearance for locking tabs of endplate inserter 900to pass through when disengaging the inserter 900 from the spinal fusionimplant 600 after it has been assembled. As shown in FIG. 50B, thesloped wall 820 of the protrusion 810 forms an angle 857 with the topsurface of the spacer and the back wall 830 of the protrusion 810 formsan angle 863 with the top surface of the spacer. In certain embodiments,the angle 857 is in the range of about 120-170 degrees, preferably135-160 degrees, and the angle 863 is in the range of 95-135 degrees,preferably 105-120 degrees. In another embodiment the angle 863 is 90degrees and does not allow the spacer to be disengaged from theendplates when a force is applied to spacer 800 in the directionopposite in which it was inserter into the endplates 700.

FIGS. 51-56 show the approach and instrumentation used to assembleendplates 700 and spacer 800 to form spinal fusion implant 600. FIGS. 51and 52 generally show the lateral approach used to insert the endplates700 into a disc space using the endplate inserter 900. FIG. 53 shows thespacer 800 locked with the spacer inserter 914. FIGS. 54 and 55 show thespacer inserter 914 entering the lumen in the handle of endplateinserter 900 thus guiding the spacer 800 into the proper positionbetween the two endplates 700. FIG. 56 shows the slap-hammer 960 coupledwith the endplate inserter 900, to allow an impulse force to be appliedto the endplate inserter 900 to decouple the inserter from the endplates700 of the assembled spinal fusion implant 600. Force is applied in adirection away from the spine.

FIGS. 57 and 58 show an embodiment of a spacer 1000 containing analternate mechanism used to lock the spacer with the endplates of thespinal fusion device. FIG. 59 shows an isometric view of the rotatingpin 1020 having a cylindrical body 1025 and a protruding tab 1030. Eachof the sliding ends 50 and 52 of spacer 1000 contain a channel 1010which is used to house the rotating pin 1020. A capture pin 1040 may beused to interact with a slot 1080 on the rotating pin 1020 to keep therotating pin 1020 contained in the channel 1010 of sliding ends 50 and52. The spacer also contains a tapered slot 1050 which has a minimumopening which is smaller than the thickness 1060 of the protruding tab1030. The tapered slot provides a resistance for the tab fromunintentionally rotating into the unlocked, or horizontal position. FIG.60 show a picture of the tabs 1030 in the unlocked or horizontalposition In this embodiment, the rotating pin 1020 contains a femaleTORX® hole 1070 for interface with a male TORX® driver. A person skilledin the art would understand that other types of hole/slot and drivercombinations may be used. It is also possible to use a male protrusionon rotating pin 1020 and a corresponding female driver.

FIG. 61 shows a top view of an alternate endplate 1100 design thatinterfaces with spacer 1000. Endplate 1100 contains a slot 1110 used tointerface with tab 1030 on rotating pin 1020. The slot 1110 has asurface 1120 that acts as a stop when the tab 1030 is rotated clockwiseinto the vertical or locked position. This surface prevents the spacerfrom translation in the anterior direction, thus preventing the spacerfrom unintentional disengagement from the endplates.

With the tabs in the unlocked position as shown in FIG. 60, the spacer1000 may be inserted between the endplates 1100 without resistance fromthe tabs 1030. Once the spacer has been fully seated within theendplates, the rotating pins 1020 may be individually rotated clockwiseto place the protruding tabs 1030 into a vertical or locked position.FIG. 62 shows an isometric view of the endplates assembled with thespacer while the tabs 1030 are in the locked position.

The spacer 1000 may be unlocked from the endplates 1100 by rotating thepin 1020 counterclockwise, or in the opposite direction used to placethe tabs 1030 in the vertical locked position. FIG. 63 shows anisometric view of the endplates assembled with the spacer while the tabs1030 are in the unlocked position.

FIG. 64 shows and isometric view of an embodiment of a spacer 1200containing an alternate mechanism used to lock the spacer with theendplates of the spinal fusion device. Each of the sliding ends 50 and52 of spacer 1200 contains a cavity 1250 which houses a spring loadedplunger mechanism 1210.

FIG. 65 shows an exploded front view of an embodiment of a spacer 1200and the spring loaded plunger mechanism 1210. The spring loaded plungermechanism includes a plunger 1220, capture pin 1230, and a compressionspring 1240. Alternatively the compression spring could be replaced witha multi-wave compression spring, a curved disc spring, Bellevillewashers, or disc springs or other spring-like mechanism or series ofspring-like mechanisms.

FIG. 66 shows an exploded isometric view of the spacer 1200. A pocket1250 is shown on sliding end 52. The pocket encloses the plunger 1220and compression spring 1240. The capture pin 1230 is used to keepplunger captured within the cavity 1250.

FIG. 67 shows an exploded isometric view of the spring loaded plungermechanism 1210. The plunger 1220 has a slot 1260 which allows theplunger to translate over the capture pin 1230 in the verticaldirection. The plunger 1220 has a sloped surface 1270 that provides agradual lead-in to the dovetail surface 84 on the endplate when thespacer 1200 is inserted between the endplates. The sloped surfaces 1270and 1280 may be replaced by a spherical surface, as in a ball, apyramid-like surface, or a rectangular surface. The lead-in and trailingedges may be gradually sloped, as shown in surfaces 1270 and 1280, orthey may be straight up and down. As the spacer 1200 enters the dovetailsurface 84 of the endplate, the dovetail surface provides a force thatpushes the plunger 1220 into the cavity 1250, compressing the spring1240. As the spacer moves in a posterior direction within the endplates,the sloped surface 1270 of plunger 1220 enters pocket 38 of theendplate. The force from the compressed spring 1240 pushes the plungerup into the pocket 38 of the endplate. The surface 1280 of the plungerinterfaces with the edge of the pocket 38 to resist translational motionin the direction opposite of insertion.

FIG. 68 shows a top view of the assembled interbody fusion implant withthe spacer 1200 locked with the endplates using the spring loadedplunger mechanism 1210.

FIG. 69 shows an isometric view of another embodiment of a spacer 1300containing an alternate mechanism used to lock the spacer with theendplates of the spinal fusion device. Each of the sliding ends 50 and52 of spacer 1300 contain a cavity 1350 which houses a spring loadedplunger mechanism 1310. Each of the sliding ends 50 and 52 also containsa cavity 1385 for receiving a position pin 1305. The cavity 1385 may bethreaded to interface with external threads 1315 on position pin 1305.

FIG. 70 shows an exploded isometric view of the spring loaded plungermechanism 1310. The spring loaded plunger mechanism includes a plunger1320, capture pin 1330, and a compression spring 1340. Alternatively thecompression spring could be replaced with a multi-wave compressionspring, a curved disc spring, Belleville washers, or disc springs or anyother spring-like mechanism or series of spring-like mechanisms.

The plunger 1320 has a slot 1360 which allows the plunger to translateover the capture pin 1330 in the vertical direction. The plunger 1320has a sloped surface 1370 that provides a gradual lead-in to thedovetail surface 84 on the endplate when the spacer 1300 is insertedbetween the endplates. The sloped surfaces 1370 and 1380 may be replacedby a spherical surface, as in a ball, a pyramid-like surface, or arectangular surface. The lead-in and trailing edges may be graduallysloped, as shown in surfaces 1370 and 1380, or they may be straight upand down. The plunger 1320 contains a cavity 1390 which interfaces withthe lead-in boss 1395 of the position pin 1305.

FIG. 71 shows an isometric view of the spacer 1300 with the positionpins 1305 fully engaged with both the spacer and the plunger 1320. Whenthe lead boss 1395 of the position pin 1305 is engaged with the cavity1390 of plunger 1320, the lead-in surface 1370 of the plunger is in aposition such that it remains below the surface of sliding ends 50 and52 of spacer 1300. This allows the spacer to be inserted between theendplates without any resistance from the spring loaded plungermechanism 1310. The spacer may be removed from the endplates by pullingon it in a direction that is opposite to the insertion direction. Withthe position pins 1305 still in place as shown in FIGS. 72 and 73, theplunger mechanism 1310 would not resist the pullout force. The inserter114 may be removed from the spacer 1300 with the position pins 1305still engaged with the spacer 1300 and plunger 1320. With the positionpins 1305 still engaged with the plunger 1320 the spacer 1300 is notlocked with the endplates.

Position pins 1305 may be designed in such a way as to be guided throughor along spacer inserter 114 before they engage the cavity 1390 of theplunger 1320. With this design, the spacer inserter 114 guides theposition pins 1305 into their proper orientation and position. Positionpins 1305 may also be designed as a permanent extension to spacerinserter 114 as opposed to separate pieces as shown. Spacer inserter 114may be designed in such a way to allow the endplate inserter 100 to beremoved from the endplates while the spacer inserter 114 is stillengaged with the spacer 1300. This design feature would provide theflexibility to engage the plunger 1320 with the cavity 38 of theendplate, thus locking the spacer to the endplate, either before orafter the endplate inserter is disengaged from the endplates.

FIG. 74 shows an isometric view of the spacer 1300 assembled with theendplates with the position pins 1305 removed. Once the position pin1305 is removed from the cavity 1390 of the plunger 1320, the force fromthe compressed spring 1340 will push the plunger into the cavity 38 ofthe endplate. The surface 1380 of the plunger interfaces with the edgeof the pocket 38 to resist translational motion in the directionopposite of insertion.

Another aspect of the present invention is directed to a method forimplanting the spinal fusion device in a subject. The method comprisesthe steps of (1) preparing a disc space between two adjacent vertebrae;(2) inserting a first endplate and a second endplate into the discspace, wherein each endplate comprises an anterior end, a posterior end,a locking recess, and spikes on an outer surface; (3) inserting a spacerbetween said pair of endplates, wherein the spacer comprises an anteriorend, a posterior end, a first surface that engages with the firstendplate, a second surface that engages with the second endplate, afirst lateral side, a second lateral side opposite to the first lateralside, and a spring-loaded plunger having a plunger end protruding fromthe first lateral side; and (4) advancing the spacer towards theposterior end of the endplates until the plunger end self-locks into thelocking recess on at least one of the first end plate and the second endplate.

In one embodiment, the second lateral side of the spacer furthercomprises a second spring-loaded plunger having a plunger end protrudingfrom the second lateral side.

In another embodiment, the plunger end self-locks into the lockingrecess on both the first end plate and the second end plate.

FIG. 75 shows an isometric view of an embodiment of a spacer 1400containing an alternate mechanism used to lock the spacer with theendplates of the spinal fusion device. Below each of the sliding ends1450 and 1452 of spacer 1400 is a cavity 1455 which houses a springloaded plunger mechanism 1410. The opening of the cavity 1455 is locatedon the lateral sides of each of the arms 1444, 1446. The cavity isoriented in a direction that is generally transverse to the slidingdirection as the spacer 1400 enters the endplate 1500.

FIG. 76 shows an exploded front view of an embodiment of a spacer 1400and the spring loaded plunger mechanism 1410. The spring loaded plungermechanism includes a plunger 1420, capture pin 1430, and a compressionspring 1440. Alternatively the compression spring could be replaced witha multi-wave compression spring, a curved disc spring, Bellevillewashers, or disc springs or other spring-like mechanism or series ofspring-like mechanisms.

FIG. 77 shows an exploded isometric view of the spacer 1400. A cavity1455 is shown on lateral arm 1446. The pocket encloses the plunger 1420and compression spring 1440. The capture pin 1430 is used to keepplunger captured within the cavity 1455.

FIG. 78 shows an isometric view of the bottom of endplate 1500. Theendplate contains a leading edge of a dovetail 1510 and a slot 1520located on one lateral side 1542.

FIG. 79 shows an exploded isometric view of the spring loaded plungermechanism 1410. The plunger 1420 has a slot 1460 which allows theplunger 1420 to translate over the capture pin 1430 in the lateraldirection. The plunger 1420 has a plunger end 1425 with a sloped frontsurface 1470 that provides a gradual lead-in to the slot 1520 on theendplate 1500 when the spacer 1400 is inserted between the endplates. Inthis embodiment, the plunger 1420 also has a trailing surface 1480 thatis sloped to allow the spacer 1400 to be disengaged from the endplates1500 when a force is applied to spacer 1400 in the posterior-to-anteriordirection. In certain embodiments, the sloped front surface 1470 formsan angle in the range of about 120-170 degrees, preferably 135-160degrees, with the plunger end surface 1490 and the trailing surface 1480forms an angle in the range of 95-135 degrees, preferably 105-120degrees, with the plunger end surface 1490. In another embodiment, thetrailing surface 1480 forms an angle of about 90 degrees with theplunger end surface 1490 and does not allow the spacer 1400 to bedisengaged from the endplates 1500 when a force is applied to spacer1400 in the posterior-to-anterior direction. In some embodiments, thesloped surfaces 1470 and 1480 are replaced by a spherical surface, as ina ball, a pyramid-like surface, or a rectangular surface. In some otherembodiments, the lead-in and trailing edges are gradually sloped, asshown in surfaces 1470 and 1480. In yet other embodiments, the lead-inand trailing edges are generally perpendicular to the plunger face 1490.As the spacer 1400 enters the dovetail surface 1584 of the endplate1500, the leading edge 1510 of the dovetail provides a resistance forcethat pushes the plunger 1420 into the cavity 1455 in a direction towardsthe center of the spacer 1400, compressing the spring 1440. As thespacer moves in a posterior direction within the endplates, the slopedsurface 1470 of plunger 1420 enters slot 1520 of the endplate. The forcefrom the compressed spring 1440 fully engages the plunger end 1425 withthe slot 1520 of the endplate 1500. In other words, the plunger end 1425self-locks into the slot 1520 of the endplate 1500 when the spacer 1400is advanced to a position that allows the sloped surface 1470 of plungerend 1425 to enter slot 1520 of the endplate 1500. The locking processoccurs spontaneously due to the action of the compression spring 1440 ofthe spring loaded plunger mechanism 1410 and no additional steps areneeded to lock the spacer 1400 to the end plates 1500. The trailingsurface 1480 of the plunger interfaces with the edge of the slot 1520 toresist translational motion in the direction opposite of insertion.

FIG. 80 shows an isometric view of the assembled interbody fusionimplant with the spacer 1400 locked with the endplates 1500 using thespring loaded plunger mechanism 1410.

FIG. 81 shows a side view of the assembled interbody fusion implant withthe spacer 1400 locked with the endplates 1500 using the spring loadedplunger mechanism 1410.

FIG. 82 shows an exploded isometric view of another spacer 1600. Acavity 1650 is shown on lateral arm 1646. The pocket encloses theplunger 1620 and compression spring 1640. The capture pin 1630 is usedto keep plunger captured within the cavity 1650. The spacer has a cutout1655 to provide access to instrumentation which can be used to dispensebone graft or a bone graft substitute into the main cavity 1665 of thespacer 1600 after the interbody fusion device has been assembled in thedisc space.

FIG. 83 shows an isometric view of the bottom of endplate 1700. Theendplate contains a leading edge of a dovetail 1710 and a slot 1720located on each lateral side 1740, 1742.

FIG. 84 shows an exploded isometric view of the spring loaded plungermechanism 1610. The plunger 1620 has a slot 1660 which allows theplunger to translate over the capture pin 1630 in the lateral direction.The plunger 1620 has a plunger end 1625 with a sloped surface 1670 thatprovides a gradual lead-in to the slot 1720 on both endplates 1700 whenthe spacer 1600 is inserted between the endplates. The sloped surfaces1670 and 1680 may be replaced by a spherical surface, as in a ball, apyramid-like surface, or a rectangular surface. The lead-in and trailingedges may be gradually sloped, as shown in surfaces 1670 and 1680, orthey may be generally perpendicular to the plunger face 1690. As thespacer 1600 enters the dovetail surface 1784 of the endplate 1700, theleading edge 1610 of the dovetail provides a force that pushes theplunger 1620 into the cavity 1650 in a direction towards the center ofthe spacer 1600, compressing the spring 1640. As the spacer moves in aposterior direction within the endplates, the sloped surface 1670 ofplunger 1620 enters slot 1720 of the endplate. The force from thecompressed spring 1640 fully engages the plunger with the slot 1720 ofthe endplate 1700. The trailing surface 1680 of the plunger interfaceswith the edge of the slot 1720 to resist translational motion in thedirection opposite of insertion. Surfaces 1670 and 1680 extend beyondthe diameter of the plunger 1620 in two places to interface with theslot 1720 on endplate 1700 to lock the spacer 1600 to both the superiorand inferior endplates 1700 on each lateral side.

FIGS. 85 and 86 show views of the assembled interbody fusion implant1750 with the spacer 1600 locked with the endplates 1700 using thespring loaded plunger mechanism 1610. Each spring loaded plungermechanism 1610 engages with both superior and inferior endplates 1700.FIG. 85 shows passageway or channel 1655 which provides access to thecentral cavity 1665 of spacer 1600 to allow bone graft or bone graftsubstitutes to be inserted after assembly.

Alternatively, the spring loaded plunger mechanism may be replaced witha single, or multiple piece cantilever that releasably engages with thelateral slots on either the inferior or superior endplates, or both theinferior and superior endplates. The protrusion on the cantilever arm ofthe spacer moves in a direction that is generally transverse to thesliding direction as the spacer enters the endplates.

FIG. 87 shows a view of a bone graft delivery system 2000 which may beused to fill an interbody fusion implant after it has been properlypositioned and assembled in the disc space. The bone graft deliverysystem incorporates a vial 2020 which contains the bone graft or bonegraft substitute. The vial is loaded onto and releasably retained by thebone graft dispensing device. FIG. 88 shows the vial 2020 released fromthe dispensing device 2000. The distal end of the vial 2020, contains areleasably retained tube 2025 which interfaces with the interbody fusiondevice to transfer the bone graft from the vial into the interbodyimplant, thus filling it completely with bone graft. FIGS. 89 and 90show views of the bone graft delivery system 2000 interfaced with anassembled implant 1750. The tube 2025 fits into the cavity 1665 of theimplant 1750 and allows the bone graft to be injected into the implantcavity.

Referring to FIG. 88, as the handle 2005 is squeezed the rod 2010 movesin the distal direction into the vial 2020 allowing the rod cap 2015 toforce the bone graft through the tube 2025 and into the implant cavity.

FIG. 91 shows a side view of an assembled implant construct withendplates 1700, 1705 that each contains a different lordotic angle. Whentwo endplates each with different lordotic angles are used, anasymmetric implant can be constructed.

FIGS. 92 and 93 show views of an assembled extreme lateral approachimplant assembled in a disc space with the spacer 1900 locked to theendplates 1800 using a spring loaded plunger assembly 1910 andcorresponding locking recessions 1820 on the endplates 1800. FIG. 94shows an exploded isometric view of the lateral approach implant withendplates 1800 and spacer 1900.

Endplates can also be assembled with spacers in a disc space for aposterior lumbar interbody fusion, a transforaminal lumbar interbody,and an anterior cervical interbody fusion implant.

Also disclosed is a method for implanting the spinal fusion device in asubject. The method includes preparing a disc space between two adjacentvertebrae, inserting a pair of endplates into the disc space, whereineach endplate comprises an anterior end, a posterior end, a lockinghole, and spikes on an outer surface, inserting a spacer between thepair of endplates, advancing the spacer between the pair of endplatestowards the posterior end of the endplates, and rotating a rotating pinon the spacer to lock the spacer with the first endplate. The spacerincludes an anterior end, a posterior end, a first surface that engageswith the first endplate, a second surface that engages with the secondendplate, and a cavity for receiving bone graft or other materials. Inone embodiment, the method further comprises the step of inserting bonegraft or a bone substitute material into the cavity of the spacer.

Also disclosed is a method for implanting the spinal fusion device in asubject. The method includes preparing a disc space between two adjacentvertebrae, inserting a pair of endplates into the disc space, whereineach endplate comprises an anterior end, a posterior end, a lockinghole, and spikes on an outer surface, inserting a spacer between thepair of endplates, advancing the spacer between the pair of endplatestowards the posterior end of the endplates, and removing a position pinfrom the spacer to release a spring-loaded plunger that locks the spacerwith the first endplate. The spacer includes an anterior end, aposterior end, a first surface that engages with the first endplate, asecond surface that engages with the second endplate, and a cavity forreceiving bone graft or other materials. In one embodiment, the methodfurther comprises the step of inserting bone graft or a bone substitutematerial into the cavity of the spacer.

Also disclosed are spinal fusion kits that contain key components of thespinal fusion device. In one embodiment, a spinal fusion kit containsmodular endplates with different sizes and lordotic angles and modularspacers with different sizes and lordotic angles. In another embodiment,the kit further contains a endplate inserter and a spacer inserter. Inyet another embodiment, the kit further contains endplate trials ofvarious footprint and construct trials of various footprint, thickness,and lordotic angles.

It is also understood that while the present invention has beendescribed with respect to at least one embodiment, the invention can befurther modified within the spirit and scope of this disclosure. Thisapplication is therefore intended to cover any variations, uses, oradaptations of the invention using its general principles. Further, thisapplication is intended to cover such departures from the presentdisclosure as come within known or customary practice in the art towhich this invention pertains and which fall within the limits of theappended claims. Further modifications and alternative embodiments ofvarious aspects of the invention will be apparent to those skilled inthe art in view of this description. Accordingly, this description is tobe construed as illustrative only and is for the purpose of teachingthose skilled in the art of the general manner of carrying out theinvention. Elements and materials may be substituted for thoseillustrated and described herein, parts and processes may be reversed,and certain features of the invention may be utilized independently, allas would be apparent to one skilled in the art of having the benefit ofthis description of the invention. Changes may be made to the elementsdescribed herein without departing from the spirit and scope of theinvention as described in the following claims.

1. A spinal fusion device, comprising: a first endplate configured forfitting within a disc space and engaging with a first vertebra, saidfirst endplate has an anterior end and a posterior end; a secondendplate configured for fitting within said disc space and engaging witha second vertebra, said second endplate has an anterior end and aposterior end; and a single spacer configured for sliding between saidfirst and said second endplates in an anterior to posterior direction,causing said endplates to be separated in a direction generallyperpendicular to said sliding direction, wherein said spacer comprises:an anterior end; a posterior end; a first lateral side; a second lateralside, opposite to said first lateral side; a first surface that engageswith said first endplate; a second surface that is opposite to saidfirst surface and engages with said second endplate; and wherein saidfirst endplate is locked to said spacer by a locking device comprising aspring-loaded plunger in said spacer and a corresponding recess in saidfirst endplate and wherein said spring-loaded plunger protrudes fromsaid first lateral side of said spacer.
 2. The spinal fusion device ofclaim 1, wherein said spring-loaded plunger comprises a plunger body, aspring, and a slot on said plunger body that interacts with a capturepin in said spacer to keep said plunger assembled with said spacer. 3.The spinal fusion device of claim 2, wherein said plunger body comprisesa plunger end that interacts with said recess in said first endplate,and wherein said plunger end comprises an end surface and a protrusionon said end surface, said protrusion comprises a sloped front surfacethat allows said protrusion to be pushed into said recess and a trailingsurface.
 4. The spinal fusion device of claim 3, wherein said slopedfront surface of said protrusion forms an angle of about 120 degree toabout 170 degree with said end surface of said plunger body.
 5. Thespinal fusion device of claim 4, wherein said sloped front surface ofsaid protrusion forms an angle of about 135 degree to about 160 degreewith said end surface.
 6. The spinal fusion device of claim 4, whereinsaid trailing surface of said protrusion is a sloped surface that allowssaid protrusion to be pulled out from said recess in said firstendplate.
 7. The spinal fusion device of claim 6, wherein said trailingsurface of said protrusion forms an angle of about 95 degree to about120 degree with said end surface.
 8. The spinal fusion device of claim4, wherein said trailing surface of said protrusion is a surface that isgenerally perpendicular to said end surface.
 9. The spinal fusion deviceof claim 1, wherein said spacer is locked to said first and second endplates to form an assembled implant with a central cavity, and whereinthe assembled implant comprises an access channel that allows a bonegraft delivery system to inject bone graft or a bone graft substituteinto the central cavity of the assembled implant.
 10. The spinal fusiondevice of claim 1, wherein said spacer has an uneven thickness betweenthe said anterior and posterior ends that maintains a desired lordoticangle between said first and second vertebrae.
 11. The spinal fusiondevice of claim 1, wherein said first end plate has an uneven thicknessbetween said anterior and posterior ends so as to form a lordotic angle.12. The spinal fusion device of claim 11, wherein said second end platehas an uneven thickness between said anterior and posterior ends so asto form a lordotic angle.
 13. The spinal fusion device of claim 12,wherein said lordotic angle in said first end plate is the same as saidlordotic angle in said second end plate.
 14. The spinal fusion device ofclaim 12, wherein said lordotic angle in said first end plate isdifferent from said lordotic angle in said second end plate.
 15. Thespinal fusion device of claim 1, wherein said spring is selected fromthe group consisting of compression springs, multi-wave compressionsprings, curved disc springs, Belleville washers, and disc springs. 16.The spinal fusion device of claim 1, wherein said second endplate islocked to said spacer by said locking device and a corresponding recessin said second endplate.
 17. The spinal fusion device of claim 1,wherein said second endplate is locked to said spacer by another lockingdevice comprising a spring-loaded plunger in said spacer and acorresponding recess in said second endplate.
 18. The spinal fusiondevice of claim 17, wherein said spring-loaded plunger of said anotherlocking device protrudes from said second lateral side of said spacer.19. A method for implanting the spinal fusion device in a subject,comprising: preparing a disc space between two adjacent vertebrae;inserting a first endplate and a second endplate into said disc space,wherein each endplate comprises an anterior end, a posterior end, alocking recess, and spikes on an outer surface; inserting a spacerbetween said pair of endplates, wherein said spacer comprises ananterior end, a posterior end, a first surface that engages with saidfirst endplate, a second surface that engages with said second endplate,a first lateral side, a second lateral side opposite to said firstlateral side, and a spring-loaded plunger having a plunger endprotruding from said first lateral side; and advancing said spacerbetween said pair of endplates towards the posterior end of saidendplates until said plunger end self-locks into said locking recess onat least one of said first end plate and said second end plate.
 20. Themethod of claim 19, wherein said plunger end self-locks into saidlocking recess on both said first end plate and said second end plate.